1. Field of the Invention
The present invention relates to the reproduction of information from recording mediums having address signals thereon and, more particularly, to providing address signals that can be used to synchronize the playback of recording mediums recorded in different formats.
2. Description of the Prior Art
Techniques for recording analog information, such as audio signals, in digital form on various recording mediums are well known. For example, in pulse code modulation, or PCM, the analog signal is sampled at a particular sampling frequency and to each sample a value is assigned that is representative of the magnitude of the analog signal at that particular time. Those values are converted to digital data and recorded on a recording medium. With the familiar longitudinally extending magnetic tape, there are various PCM recording formats. A typical variant between formats is the number of data tracks per analog signal channel. For example, in one format the digital information might be recorded in one track on the tape comprising a series of data blocks consecutively arranged on the tape. In another format the tape could have four parallel, adjacent tracks per channel.
Different formats used for PCM recording are shown in detail in U.S. patent application Ser. No. 286,963, filed July 27, 1981, now U.S. Pat. No. 4,389,681, issued June 21, 1983, and assigned to the assignee of the present invention. As that application shows, a one track/analog channel format arranges the digital information into uniform data blocks and simply records them one after the other on a tape passing a magnetic recording head. The four track/analog channel format records the digital data, arranged in similar data blocks, simultaneously in four adjacent data blocks. The advantages of that particular arrangement are discussed in the patent application cited above.
Another feature of digital recording is the ability to provide convenient retrieval of information on the tape. Each consecutive group, or sector, of data blocks is given a digital address and, by incrementing each sector address as the signal is recorded, any particular group of data blocks can be found by searching for its assigned address.
In the above-cited patent application, the sector addresses are incremented by a predetermined amount regardless of format. However, that complicates the synchronization of the playback of two tapes recorded in different formats because the playback speeds, which correspond to the respective recording speeds, are different. In the example given above, the sector addresses of the tape recorded in the one track/channel format increase four times as fast as those of the tape recorded in the four track per channel format, and a synchronization circuit would be extremely complex.